Monday, December 13, 2010

What is the sensitivity and specificity of a CT scan of the chest for detecting mediastinal involvement in a patient with non-small cell lung cancer?

What about a PET scan?

Palliative medicine practitioners frequently see patients with stage IV lung cancer. Usually the stage has been fully elucidated prior to the initial palliative care consultation, but not always. Admittedly, this biased my assumptions about the sensitivity/specificity of these tests and I would have guessed much higher than the actual answers (even though I knew neither was 100% sensitive).

CT scan of the chest to diagnose mediastinal disease in NSCLC: Sensitivity 51% and specificity 85%.

PET scan: Sensitivity 74% and specificity 85%.

The current gold standard for diagnosing mediastinal involvement (prior to proceeding with a thoracotomy for possibly resectable disease) is a mediastinoscopy. Mediastinoscopy can help reduce the rate of thoracotomies by diagnosing metastases not detected via imaging. A recent randomized controlled trial published in JAMAsuggests that a combined approach of endoluminal ultrasound guided fine needle aspiration (EUS-FNA) plus endobronchial ultrasound guided transbronchial aspiration (EBUS-TBNA) may provide equal or greater sensitivity compared to mediastinoscopy. This may result in fewer unnecessary thoracotomies (where the patient was found to be unresectable during the thoracotomy). The rate of unnecessary thoracotomies was significantly reduced if patients who had negative endoscopies underwent mediastinoscopy. (Wow- that's a lot of tests: CT scan (negative)-->PET(negative)-->EUS/EBUS(negative)-->mediastinoscopy.)

In a related editorial, the author points out that the use of this diagnostic modality would be limited to centers where there is expertise in both EUS and EBUS.

I wanted to mention this study briefly to draw attention to the dilemma facing patients with possibly resectable disease. While it's not the most common scenario that the palliative care practitioner faces, occasionally there will be patients with seemingly earlier stage disease who have significant symptoms or psychosocial issues that lead to a palliative care consult. Or perhaps the patient has significant COPD that complicates the situation. I'll hypothesize that the decision of whether to proceed with a thoracotomy in these types of patients is more challenging for both the patient and the health care team. Through having an understanding of the staging dilemmas, a palliative care consultant can work with the oncologist and thoracic surgeon to help guide the patient through the decision.

Pallimed: A Hospice & Palliative Medicine Blog Founded June 8, 2005.
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